This invention relates to an instrument for excising a portion of a suspected lesion which is desired to be biopsied for determination of malignancy. More specifically, it relates to such an instrument which can perform the excision and remove the excised tissue in a minimally invasive manner.
Statistics currently reveal that one in nine American women will develop breast cancer. It is the leading cause of cancer deaths in women between the ages of 40-55, and the second leading cause of cancer deaths in women overall. Unfortunately, breast cancer will only be diagnosed in about one in eight women, and one in thirty will die of this disease. Breast cancer does occur in men but it is much uncommon.
A biopsy of the breast is often indicated if suspicious tissue is detected. Biopsy requests stem from a screening process generally performed via a physical examination to detect a palpable lesion or a mammogram for the detection of a nonpalpable lesion. Five out of six biopsies performed return benign indications.
The goal of the biopsy is the discovery and accurate diagnosis of benignity or malignancy of suspect tissue. Survival rates are significantly greater with early detection. However, as detection is attempted in earlier stages of carcinoma development, accurate sampling of the lesion becomes more difficult due to small lesion size. Ideally, a sufficiently large sample size is taken to accurately diagnosis disease state with minimal trauma (physical deformity or scarring) to the patient.
The current standard for care is a significantly invasive procedure known as "Open Excisional Biopsy". Prior to an open excisional biopsy for a nonpalpable mass, an interventional radiologist will initially take mammograms to place a guidewire which directs the surgeon to the area of excision. Mammograms are then taken to assure that the guidewire is accurately placed in or near the desired biopsy site. The guidewire has a barbed end in order maintain its position at the desired site and is fed through an elongated needle.
The general surgeon applies local or, more commonly, general anesthesia, during an open excisional biopsy. Dissection is made through the skin and subcutaneous fat and the flap is undercut and retracted. Incision length, during an open excisional biopsy generally runs between 2-5 inches and is dependent on the location of the lesion, breast characteristics, and surgeon technique. The breast parenchyma is then dissected along the guidewire until the site of the specimen is exposed. The specimen, generally spherical in shape centered about the barbed end of the guidewire, and roughly 1 inch in diameter, is manually excised.
The specimen size taken during an open excisional biopsy is adequate, however deformation (scarring and subsequent shape of the breast) and potential "seeding" of the cancerous cells is often a large concern. Accuracy is generally acceptable, however the guidewire often moves from its original position during the excisional process leading to decreased accuracy and the need for larger specimens.
New technologies are being developed to assist the early detection of breast cancer. The technologies are primarily focused on imaging of nonpalpable tissue and accessing the tissue with minimally invasive techniques for biopsy. The cost and trauma associated with open excisional biopsy is minimized with these technologies.
The two primary imaging technologies for assisting minimally invasive breast biopsy of a nonpalpable mass are ultrasound and stereotactic X-rays. Ultrasound accurately guides a hand-held core biopsy needle (CBN) to the biopsy site. Stereotactic imaging is performed with the patient lying prone on a stereotactic table and X-rays are taken at 15 degrees off-axis on each side of the breast. The X-rays are fed into a digital signal imaging system to create a 3-D reference; the location for biopsy is triangulated and coordinates are fed to the stereotactic table.
The actual specimen removal in the minimally invasive approach is performed in any one of the following ways.
TruCut.RTM. Needle Method--The "TruCut" needle method utilizes a small diameter needle which is inserted to a desired depth, actuated, and removed. The product for practicing this method has two co-axial tubular members. The outer member is retracted exposing a lateral opening in the inner member. The elastic property of the tissue causes tissue to enter the hollow core of the inner member. The outer member is then advanced forward, shearing the tissue sample which has been trapped in the inner member. Inherent disadvantages to this technique are the need for multiple insertions with questionable accuracy and extremely limited tissue sample sizes.
Surface to Site Core Sampling (SSCS)--The SSCS method attempts to maximize accuracy through the increase in sample size while maintaining controlled guidance. A cylindrical cutting tube is advanced through an opening in the skin. As it moves forward, it creates a continuous cylindrical core sample until it reaches the depth desired by the surgeon. Upon completion of the linear motion, the distal end of the sample is transected, and the device is withdrawn with the sample within the cutting element. The critical disadvantage to this approach is the trauma and disfigurement associated with excision of the healthy tissue superior to the site of questionable tissue.
Percutaneous Core Biopsy (PCB)--The PCB method attempts to obtain the advantages of single insertion and large sample size of the SSCS approach, while minimizing disfigurement as achieved by the TruCut.RTM. needle method. As in the case of a TruCut.RTM. needle device, the PCB has multiple co-axial tubular members. However, one of the members remains stationary, eliminating the need for multiple insertions. Samples are obtained in a controlled contiguous manner which ultimately achieves the desire for obtaining large tissue samples at the questionable site.
Another recent minimally invasive approach for excising a portion of a targeted lesion is described in U.S. Pat. No. 5,526,822. The biopsy apparatus described in this patent has an outer biopsy cannula with a penetrating member for positioning adjacent the targeted lesion. The biopsy cannula has a lateral tissue receiving port, and a vacuum is drawn through the port for pulling tissue into the port. An inner cutting cannula moves forwardly to excise the tissue received in the port. With the aid of a vacuum drawn on the inner cutting cannula, the inner cutting cannula retains the excised tissue as the inner cannula is retracted for tissue removal, and the outer biopsy cannula remains stationary. Following removal, the outer biopsy cannula can be rotated relative to a fixed housing, and multiple samples can therefore be taken circumferentially without the need for multiple insertions and withdrawals of the biopsy cannula. The biopsy apparatus and its method of use as described in the '822 patent are exemplified in the Mammotome.RTM. Breast Biopsy System.
In addition to biopsy instruments which contain lateral receiving ports for receiving tissue which is subsequently severed with a cutter, additional mechanisms have been disclosed to excise the tissue from the targeted lesion. For example, U.S. Pat. No. 4,177,797 describes a tissue cutter with a sharp helical thread along a needle which rotates into the tissue. An outer hollow cylindrical cutting tube slides over the needle to cut the tissue. The tissue is trapped between the inner diameter of the cutter and the threaded needle. The excised tissue is then retrieved by removal of the threaded needle and cutting tube simultaneously.
Unfortunately, the sample size obtained is limited because of the limited space between the solid needle and the tissue cutter. A limited sample size requires the user to take significantly more samples, thus increasing procedural time and cost.
Another disadvantage with the device described in the '797 patent is that it "cores" all of the tissue from the skin surface to the interior biopsy site. The device does not permit sampling only at the target location and therefore results in removing healthy tissue.
U.S. Pat. No. 4,682,606 discloses a biopsy apparatus which utilizes a corkscrew mechanism to hold tissue and allow guidance of a cutting instrument which will excise the tissue. The corkscrew mechanism includes a hollow shaft through which a guide extension rod and guided needle can be inserted. The cutting instrument severs the tissue around the area of the corkscrew. This is accomplished by closing a jaw like mechanism at the distal end of the cutting instrument. In addition to the disadvantage of limited sampling as described in connection with the '797 patent above, this particular device also suffers from the disadvantage in that it only allows superficial sampling of the tissue.
U.S. Pat. No. 5,047,040 discloses an atherectomy device and method for removing stenosis material from a vessel by inserting a rotating helical auger shaped bit along a guide wire. An outer tubular cutting member is advanced so that the stenosis is severed and entrapped between the cutter and the bit. U.S. Pat. No. 5,078,723 discloses an atherectomy device for removing stenosis from arteries. A catheter body is used to deliver a stenosis to the cutter site. A screw mounted on the distal end of the body enters and holds the stenosis. An annular cutting means is moved forward around the screw to cut the stenosis which is held by the screw. The catheter is then removed with the cut stenosis trapped inside the cutter. The devices described in these patents again are limited in the sample size which can be taken, and also are restricted to the removal of tissue for limited applications such as removing stenosis material from a vessel. These devices would not be adaptable for other applications where it is desired to remove a targeted tissue mass, for example, in the breast to obtain a breast biopsy.
In view of the increasing demand for a surgical instrument to capture tissue samples for biopsy in a minimally invasive manner while concurrently excising an appropriately sized targeted tissue mass, a surgical instrument for obtaining tissue biopsies for multiple applications is needed. In particular, what is needed is a minimally invasive biopsy instrument which can readily excise a large tissue sample within the targeted tissue mass.